1. Field of the Invention
This invention relates to a air-applying device for applying, from the periphery of an impeller, the air that has been drawn into the center of an impeller. The invention also relates to a cooling unit having such an air-applying device, and to an electronic apparatus, e.g., a portable computer, which contains such an air-applying device.
2. Description of the Related Art
Electronic apparatuses, such as portable computers, incorporate a microprocessor. The microprocessor generates heat while operating. The heat it generates increases with faster processing (clock) speeds and with the number of functions performed. A conventional electronic apparatus incorporates a cooling unit that positively cools the microprocessor.
The cooling unit is provided, along with the microprocessor, in the housing of the electronic apparatus. The cooling unit includes a heat sink and a centrifugal air-applying device. The heat sink is thermally connected to the microprocessor. The air-applying device applies cooling air to the heat sink. The air-applying device has an impeller and a case containing the impeller. The impeller may be rotated. The case has an air inlet port, a spiral chamber, and an air outlet port. The air inlet port opens to the center of rotation of the impeller. The spiral chamber surrounds the impeller. The air outlet port lies at the output end of the spiral chamber, or the downstream end thereof.
When the impeller is rotated, air is drawn to the center of rotation of the impeller from the interior of the housing or from outside the housing and flows to the periphery of the impeller. The air is then applied from the periphery of the impeller into the spiral chamber, by virtue of a centrifugal force. The spiral chamber is designed to convert the velocity energy of the air applied from the impeller, into pressure energy. In the chamber, the impeller collects the air and blows the air to the air outlet port. Through the air outlet port, the air is forced onto the heat sink, acting as cooling air. As a result, the heat is radiated from the microprocessor, thanks to the heat exchange between the microprocessor and the cooling air. The heat is expelled from the housing as the air flows from the housing.
In the air-applying device, the air flows from the periphery of the impeller into the spiral chamber, is collected in the chamber and supplied to the air outlet port. Therefore, the air pressure in the spiral chamber gradually increases from the input end of the chamber to the output end of the chamber. The air pressure abruptly falls at a position immediately before the outlet port. Hence, the chamber has a high-pressure region near its output end.
In the conventional air-applying device, the air inlet port, which has a perfectly circular cross section, is coaxial with the impeller and communicates with the spiral chamber. (See FIG. 10) Thus, the air in the chamber at a position that corresponds to the above-mentioned high-pressure region, may acquire a higher pressure than the air at the inlet port. If so, part of the air in the spiral chamber abruptly flows from the chamber and through the air inlet port. In other words, the air in the chamber leaks to the air inlet port of the case and may not be reliably guided from the air inlet port to the air outlet port.
Japanese Patent Application Publication (KOKAI) No. 10-326986 discloses a fan device in which air is prevented from abruptly flowing from the case to and through the air inlet port. In this fan device, a ring surrounds the impeller, guiding air to prevent an abrupt flow of air.
In the prior-art fan device, however, a ring that rotates together with the impeller and a structure that secures this ring to the blades of the impeller are necessary.
Inevitably, the impeller is complex in structure and composed of a large number of components. This increases the manufacturing cost of the fan device.
Embodiments of the present invention provide an air-applying device used in a cooling unit and/or an electronic apparatus having a heat generating component.
According to an embodiment of the present invention, an air-applying device has an impeller having a center of rotation, and a case which contains the impeller. The case includes a first edge defining an inlet port of air which exposes the center of rotation, a second edge defining an outlet port of air, and a high-pressure region which presents upon operational rotation of said impeller. The high-pressure region is located within the case along a peripheral portion of the impeller. A distance between the center of rotation of the impeller and the first edge is shorter in the direction from the center of rotation to a center of the high-pressure region than from the center of rotation to region other than the high-pressure region.
According to the other embodiment of the present invention, an air-applying device includes an impeller having a center of rotation, and a case which contains the impeller. The case has a wall defining a chamber with an initiating point, a midpoint, and a terminating point defined in order along a rotating direction of the impeller. The case also has a first edge defining an inlet port of air which exposes the center of rotation, and a second edge defining an outlet port of air. A distance between the center and the first edge is variable, and the shortest distance falls within an angular region of the chamber between the midpoint and the terminating point.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.